1. Field of the Invention
The present invention relates to a one-way clutch provided with a spring along an inner circumference of a cage, and more particularly, to the one-way clutch in which sprags can be properly urged without damaging the spring, even though an irregular repulsive force is applied to the sprags when the cage is press fitted into an outer race.
2. Description of the Related Art
Generally, in order to repeatedly conduct transmission and interruption of an engine power between an inner race and an outer race, a one-way clutch is provided between these inner race and outer race.
FIG. 6 shows a conventional one-way clutch including a cage 23 having a flange portion 23f, a spring 24, and a plurality of sprags 25. In the one-way clutch of this type, the cage 23 is often provided with a tightening margin when it is press fitted into an outer race (not shown), for the purpose of synchronously rotating the cage 23 and the outer race. For this reason, the one-way clutch is designed in such a manner that an outer diameter of the cage 23 (an outer diameter of the flange portion 23f) may be somewhat larger than an inner diameter of a track face of the outer race so as to give retaining force, when the cage is press fitted to the outer race. However, there has been a problem that the cage 23 may become off-center with s respect to the outer race due to a pressure when it is press fitted to the inner peripheral face of the outer race, and clearances between the sprags 25 and respective pockets of the cage 23 may become narrow. Under the circumstances, in order to avoid such phenomenon, it has been proposed that the flange portion 23f of the cage 23 is cut at an equal interval in a circumferential direction to form cut-outs 23c (Japanese Utility Model Registration No. 2598500). Alternatively, there has been disclosed a structure in which a cage having a somewhat elliptical shape is press fitted into an outer race so that the outer race and the cage may be integrally rotated (Japanese Utility Model Publication No. JP-B-6-10233U).
Further, it often happens in the one-way clutch that a distance of a space between the outer race and the inner race may vary in size, due to misalignment. Specifically, in case where there is a large distance between an inner peripheral face of the outer race and an outer peripheral face of the inner race, recovering force from tongue pieces of the spring will be decreased, and in case where there is a small distance between the inner peripheral face of the outer race and the outer peripheral face of the inner race, the recovering force from the tongue pieces of the spring will be increased. Such variation of the recovering force may lead to difficulty in synchronous operation of the sprags on occasion of torque transmission, and in order to overcome this difficulty, an example of the one-way clutch as shown in FIG. 7 has been proposed. Specifically, this one-way clutch includes a cage 13, a spring 14 (usually, a ribbon spring is employed) and a plurality of sprags 15, and disposed in an annular space 20 between an outer race 11 and an inner race 12 When the one-way clutch is rotated in one direction along with relative rotation of the outer race 11 and the inner race 12 on occasion of power transmission, the sprags 15 function as wedges allowing the outer race 11 and the inner race 12 to rotate integrally (locked). On the other hand, when the one-way clutch is rotated in the reverse direction, the wedge function will be released to put the one-way clutch into an idle rotation, and transmission of the power will be interrupted (unlocked). This one-way clutch is characterized in that a value of a length L of an arm after variation which is represented by a distance between a function line of a recovering force F acting at a tongue piece 14t and a perpendicular line from an edge 14a of a pocket 14p abutted against the sprag 15 as a pivotal center is set so as to be in a reciprocal proportion to a value of the recovering force F after variation caused by misalignment in a locked or a free state of the sprag 15 (Japanese Patent No. 2653040).
Generally, in the one-way clutch, a spring 34 is provided on an inner diameter side of a cage 33 which holds sprags 35, and the sprags 35 are always urged into a locked state by means of tongue pieces 34t of the spring 34, as shown in FIG. 8 and FIG. 9 which is a view as seen in a direction of arrows A—A in FIG. 8. However, when the cage 33 whose one part (around an upper part in FIG. 6) is formed in a somewhat elliptical shape in order to rotate the cage 33 synchronously with the outer race is press fitted to an inner peripheral face (a track face) 1a of the outer race 1, the spring 34 will be locally deformed toward a center in a radial direction to a large extent, especially due to a repulsive force when the elliptical part is press fitted. Consequently, as shown in FIG. 10 which is a view as seen in a direction of arrows B—B in FIG. 9, urging force of the tongue pieces 34t of the spring 34 exerted on the sprags 35 which have been preloaded by the tongue pieces 34t of the spring 34 will be decreased, and at a position where the spring has been largely deformed, an inclined posture of the sprags 35 will be promoted to come into an idle rotation. As the results, there has been such a problem that on occasion of shifting from the idle rotation to an engaged position, an count of deformation of the tongue pieces 34t of the spring may be increased, and the tongue pieces 34t will be liable to be damaged, thus causing a defective engagement of the one-way clutch.